Electronic fuel injection system

ABSTRACT

A primary control pulse is initiated in synchronization with the operation of an internal combustion engine and is terminated after a time duration Tp which is determined as a preselected function of a primary engine operating parameter. A control voltage is developed across a capacitor having a capacitance C. The capacitor is charged with a charge current Ic in response to the presence of a primary control pulse to increase the control voltage from an initial level Li to a peak level Lp. The capacitor is discharged with a discharge current Id in response to the absence of a primary control pulse to decrease the control voltage from the peak level Lp to a final level Lf. Fuel is applied to the engine in an amount proportional to the time interval established between the departure of the control voltage from the initial level Li and the arrival of the control voltage at the final level Lf. As a result, the total quantity of fuel Q delivered to the engine is defined by the following equation:

United States Patent Gambill et al.

[ Nov. 11, 1975 ELECTRONIC FUEL INJECTION SYSTEM [57] ABSTRACT [75] Inventors: Charles C. Gambill, Kokomo, lnd.; A primary control pulse is initiated in synchronization John P. McGavic, Lake Park, Fla. with the operation of an internal combustion engine [73] Assigneez General Motors Corporation, and s terminated after a time duration T,, wh1ch is de- 1 Detroit Mich termmed as a preselected function of a primary engine operating parameter. A control voltage is developed [22] Filed: Oct. 27, 1972 across a capacitor having a capacitance C. The capac- [211 App]. NO: 301,422 itor is charged w1th a charge current I in response to the presence of a primary control pulse to increase the control voltage from an initial level L to a peak level [52] US. Cl 123/32 EA L,,. The capacitor is discharged with a discharge cur- [51] Int. Cl.- F0213 3/00 rent 1,, in responseto the absence of a primary control [58] Field of Search 123/32 EA pulse to decrease the control voltage from the peak level L,, to a final level L Fuel is applied to the engine [56] q References Cited in an amount proportional to the time interval estab- UNITED STATES PATENTS lished between the departure of the control voltage 2,910,054 10/1959 Schutte 123/32 EA from the mitial level and the arrival of the control 2,982,276 5/1961 266116311 et al.... 123/32 EA Voltage at the level LP As a result the total quan' 3,456,628 7/1969 Bassot 123/32 EA y Of fuel Q delivered to the engine is defined y the 3,464,396 9/1969 Scholl 123/32 EA following equation: 3,483,851 12/1969 Reichardt... 123/32 EA 3,522,794 8/1970 Reichardt... 123/32 EA Q TI(1 11 i M (5/10 At least one of 3,593,692 7/1971 SChOll 123/32 EA the Charge Current t the discharge Current d is 3,653,365 4/1972 Monpetit 123/32 EA determined as a preselected function of a secondary 3.727.081 4/1973 Davis 123/32 EA engine operating parameter which is multiplicatively 3,734,067 5/1973 t- 123/32 EA related to the primary engine operating parameter. At 3,744,460 7/1973 Monpet1t 123/32 EA least one of the initial level L and the final level L! is I determined as a preselected function of a secondary 'W' f Myhre engine operating parameter which is additively related 4585mm Emmme" l aonald COX u to the primary engine operating parameter. Attorney, Agent, or Fzrn1T. G. .lagodzinski 4 Claims, 4 Drawing Figures are 3* ti? FUEL FUEL PUMP TANK w 2a a? 72 f 20 F*" -;;*1 z "1 w I rr Sta 1 L 1/11 w 22 74' 79 I 3 3 1 l 3 2 m 1 w m I 1 l 1 I 26 E F":\ .I i

| I a 1 L I 1 l I w y 1 8g L lGNlTl ON ,IM TIMING flag I I FUEL PULSE PULSE IN ECTOR GENERATOR GENERATOR I; DRIVER 1 2 a 1' j 82 (4a l I" 7 7 :7 l ,u w 106 98 f I w 1 [ml \FQEEELGAETOR 33 I vs I 1 I x L. PRIMARY SECONDARY 'NJECTION CONTROL CONTROL L E 1 PULSE w PULSE SYNTHE a: GENERATOR GENERATOR SIZER kg; LL-

US. Patent Nov. 11, 1975 Sheet 1 012 3,918,417

6'6 62 FUEL FUEL 50 PUMP 68 TANK I 116 56 RA a? u 7.2 I

| I 28 W118 f I J- a "I/II/I/ I 79 l 4 6 I PRESSURE I SENSOR i 52 I12 I 10 2 I I .26 O ,8 I24 I V06 I I2 I20 14 I l L i I f Q I I I I I so 82 IGNITION /4 TIMING I FUEL PULSE PULSE I INJECTOR GENERATOR GENERATOR 1 VER I 86 1 82 I '5 f f q J 106 98 I I VOLTAGE I I T REGULATOR A 8 I I 116 I /w 56 l L PRIMARY SEGONDARY INJECTION E GONTROL CONTROL PULSE E PULSE I08 PULSE SYNTI-IE- 86' GENERATOR GENERATOR SIzER CHARGE 158 U.S. Patent N0v.11, 1975 Sheet20f2 3,918,417

DISCHARGE CIRCUIT 125 ELECTRONIC FUEL INJECTION SYSTEM This invention relates to a fuel supply system for an internal combustion engine. More particularly, the invention relates to an electronic fuel injection system.

According to the invention, a control voltage is developed across a capacitor having a capacitance C. The capacitor is alternately charged and discharged in synchronization with the operation of the engine. Specifically, the capacitor is charged with a charge current I to increase the control voltage from an initial level L,- to a peak level L,, over a charge time period. Conversely, the capacitor is discharged with a discharge current I to decrease the control voltage from the peak level L,, to a final level L; over a discharge time period.

The peak level L of the control voltage is determined as a preselected function of a primary engine operating parameter such as intake air pressure. Preferably, the charge time period of the capacitor is defined by a primary control time period T,, which is regulated in response to the primary engine operating parameter thereby to indirectly determine the peak level L of the control voltage.

In addition, at least one of the charge current I and the discharge current 1,, of the capacitor is defined as a preselected function of a secondary engine operating parameter, suchas engine temperature, which is multiplicatively related to the primary engine operating parameter. Further, at least one of the initial level L, and the final level L of the control voltage is defined as a preselected function of a secondary engine operating parameter, such as battery supply voltage, which is additively related to the primary engine operating parameter.

Fuel is applied to the engine in an amount determined by the time interval established between the departure of the control voltage from the intitial level L,- and the arrival of the control voltage at the final level L,. Consequently, the total quantity of fuel Q delivered to the engine is defined by the following equation:

In relation to the primary engine operating parameter, the fuel quantity Q is definedby a linear fuel control curve characterized by a slope and an offset. The slope of the fuel control curve is determined by the preselected function of the secondary engine operating pa rameter which is multiplicatively related to the primary engine operating parameter. The offset of the fuel control curve is determined by the preselected function of the secondary engine operating parameter which is additively related to the primary engine operating parameter.

These and other aspects of the invention may be best understood by reference to the following detailed description of a preferred embodiment when considered in conjunction with the accompanying drawings. As used in equations appearing in both the specification and the claims, the symbol means is equal to while the symbol a means is proportional to.

In the drawings:

FIGS. 1 and 3 are schematic diagrams of an electronic fuel injection system incorporating the principles of the invention.

FIGS. 2 and 4 are graphic illustrations useful in explaining the operation of the electronic fuel injection system shown in FIGS. 1 and 3.

Referring to FIG. 1, an internal combustion engine It for an automotive vehicle includes a combustion chamber or cylinder 12. A piston 14 is mounted for reciprocation within the cylinder 12. A crankshaft 16 is supported for rotation within the engine 10. A connecting rod 118 is pivotally connected between the piston 14 and the crankshaft 16 for rotating the crankshaft within the engine 10 when the piston 14 is reciprocated within the cylinder 12. Conventionally, a fluid coolant is circulated over the exterior wall of the cylinder 12 by a coolant system (not shown) to dissipate excessive heat generated within the combustion chamber 12.

An intake manifold 20 is connected with the cylinder 12 through an intake port 22. An exhaust manifold 24 is connected with the cylinder 12 through an exhaust port 26. An intake valve 28 is slidably mounted within the top of the cylinder 12 in cooperation with the intake port 22 for regulating the entry of combustion ingredients into the cylinder 12 from the intake manifold 20. A spark plug 30 is mounted in the top of the cylinder 12 for igniting the combustion ingredients within the cylinder 12 when the spark plug 30 is energized. An exhaust valve 32 is slidably mounted in the top of the cylinder 12 in cooperation with the exhaust port 26 for regulating the exit of combustion products from the cylinder 12 into the exhaust manifold 24. The intake valve 28 and the exhaust valve 32 are driven through a suitable linkage 34 which conventionally includes rocker arms, lifters, and a camshaft.

An electrical power source is provided by the vehicle battery 36. An ignition switch 38 connects the battery 36 between a power line 40 and a ground line 42. When the ignition switch 38 is closed, the battery 36 applies a supply voltage to the power line 40. A conventional ignition pulse generator 44 is electrically connected to the power line 46 and is mechanically connected with the crankshaft 16 of the engine 10. Further, the ignition pulse generator 44 is connected through a spark cable 46 to the spark plug 30. In the usual manner, the ignition pulse generator 44 energizes the spark plug 30 in synchronization with the rotation of the crankshaft T16 of the engine 10. Hence, the ignition pulse generator 44 combines with the ignition switch 38 and the spark plug 30 to form an ignition system.

A fuel injector 48 includes a housing 50 having a fixed metering orifice 52. A plunger 54 is supported within the housing 50 for reciprocation between a fully opened position and a fully closed position. In the fully opened position, the forward end of the plunger 54 is opened away from the orifice 52. In the fully closed position, the forward end of the plunger 54 is closed against the orifice 52. A bias spring 56 is seated between the rearward end of the plunger 54- and the housing 50 for normally maintaining the plunger 54 in the fully closed position. A solenoid or winding 58 is electromagnetically coupled with plunger 54 for retracting the plunger 54 to the fully opened position against the action of the bias spring 56 when the winding 58 is energized. The bias spring 56 drives the plunger 54 to the fully closed position when the winding 58 is deenergized. The fuel injector 48 is mounted on the intake manifold 20 of the engine 10 for injecting fuel into the intake manifold 20 at a constant flow rate through the metering orifice 52 when the plunger 54 is in the fully opened position. Notwithstanding the illustrated structure, it is to be noted that the fuel injector 48 may be provided by any suitable voltage responsive valve.

A fuel pump 60 is connected to the fuel injector 48 by a conduit 62 and to the vehicle fuel tank 64 by a conduit 66 for pumping fuel from the fuel tank 64 to the fuel injector 48. Preferably, the fuel pump 60 is connected to the power line 40 to be electrically driven from the vehicle battery 36. Alternately, the fuel pump 60 could be connected to the crankshaft 16 to be mechanically driven from the engine 10. A pressure regulator 68 is connected to the conduit 62 by a conduit 70 and is connected to the fuel tank 64 by a conduit 72 for defining the pressure of the fuel applied to the fuel injector 48. Thus, the fuel injector 48 combines with the fuel tank 64, the fuel pump 60 and the pressure regulator 68 to form a fuel supply system.

A throttle valve 74 is rotatably mounted within the intake manifold for regulating the flow of air into the intake manifold 20 from an air supply system (not shown) in accordance with the position of the throttle valve 74. The throttle valve 74 is connected through a suitable linkage 76 with the vehicle accelerator pedal 78. The accelerator pedal 78 is pivotably mounted on a reference surface for movement against the action of a compression spring 79 seated between the accelerator pedal 78 and the reference surface. As the accelerator pedal 78 is depressed, the throttle valve 74 is moved to a more opened position to increase the flow of air into the intake manifold 20. Conversely, as the accelerator pedal 78 is released, the throttle valve 74 is moved to a less opened position to decrease the flow of air into the intake manifold 20.

In operation, fuel and air are combined within the intake manifold 20 to form an air/fuel mixture. The fuel is injected into the intake manifold 20 at a constant flow rate by the fuel injector 48 in response to energization. The precise amount of fuel deposited within the intake manifold 20 is regulated by an electronic fuel injection control system which will be described later. The air enters the intake manifold 20 from the air supply system (not shown) which conventionally includes an air filter. The precise amount of air admitted into the intake manifold 20 is determined by the position of the throttle valve 74. As previously described, the position of the accelerator pedal 78 controls the position of the throttle valve 74.

As the piston 14 initially moves downward within the cylinder 12 on the intake stroke, the intake valve 28 is opened away from the intake port 22 and the exhaust valve 32 is closed against the exhaust port 26. Accordingly, combustion ingredients in the form of the air/fuel mixture within the intake manifold 20 are drawn by negative pressure through the intake port 22 into the cylinder 12. As the piston 14 subsequently moves upward within the cylinder 12 on the compression stroke, the intake valve 28 is closed against the intake port 22 so that the air/fuel mixture is compressed between the top of the piston 14 and the top of the cylinder 12. When the piston 14 reaches the end of its upward travel on the compression stroke, the spark plug is energized by the ignition circuit 44 to ignite the air/fuel mixture. The ignition of the air/fuel mixture starts a combustion reaction which drives the piston 14 downward within the cylinder 12 on the power stroke. As the piston 14 again moves upward within the cylinder 12 on the exhaust stroke, the exhaust valve 32 is opened away from the exhaust port 26. As a result, the combustion products in the form of various exhaust gases are pushed by positive pressure out of the cylinder 12 through the exhaust port 26 into the exhaust manifold 4 24. The exhaust gases pass out of the exhaust manifold 24 into the exhaust system (not shown) which conventionally includes a muffler and an exhaust pipe.

Although the structure and operation of only a single combustion chamber or cylinder 12 has been described, it will be readily appreciated that the illustrated internal combustion engine 10 may include additional cylinders 12 as desired. Similarly, additional fuel injectors 48 may be provided as required. However, as long as the fuel injectors 48 are mounted on the intake manifold 20, the number of additional fuel injectors 48 need not necessarily bear any fixed relation to the number of additional cylinders 12. Alternately, the fuel injector 48 may be directly mounted on the cylinder 12 so as to inject fuel directly into the cylinder 12. In such instance, the number of additional fuel injectors 48 would necessarily equal the number of additional cylinders 12.

A timing pulse generator 80 is connected with the crankshaft 16 for developing rectangular timing pulses having a frequency which is proportional to and synchronized with the rotating speed of the crankshaft 16. The rectangular timing pulses produced by the timing pulse generator 80 are applied to a timing pulse line 82. Preferably, the timing pulse generator 80 is provided by an inductive speed transducer coupled with a bistable switch.

An injection pulse generator 84 is coupled with the engine 10 for developing rectangular injection pulses having a length determined as a function of several different engine operating parameters. The injection pulses produced by the injection pulse generator 84 are synchronized with the timing pulses produced by the timing pulse generator 80. The injection pulses are applied by the injection pulse generator 84 to an injection pulse line 86. The injection pulse generator 84 will be more fully described later.

A fuel injector driver 88 is connected with the timing pulse line 82 and with the injection pulse line 86. Further, the fuel injector driver is connected through an injection drive line 90 to the fuel injector 48 and is connected to the vehicle battery 36 through the power line 40 and the ignition switch 38. The fuel injector driver 88 is responsive to the occurrence of the timing pulses produced by the timing pulse generator 80 to energize the fuel injector 48. The time period for which the fuel injector 48 is energized by the fuel injector driver 88 is defined by the length or duration of the injection pulses produced by the injection pulse generator 84. In other words, the fuel injector driver 88 is responsive to the coincidence of a timing pulse and an injection pulse to energize the fuel injector 48 for the duration of the injection pulse.

The fuel injector driver 88 may be virtually any logic switch or amplifier capable of executing the desired coincident pulse operation. However, where additional fuel injectors 48 are provided, it may be necessary that the fuel injector driver 88 also select which one or ones of the fuel injectors 48 are to be energized in response to each respective timing pulse. As an example, the fuel injectors 48 may be divided into separate groups which are successively energized in response to succeeding ones of the timing pulses. Conversely, the timing pulses may be applied to a logic network which selects the fuel injectors 48 for individual energization.

The injection pulse generator 84 comprises a primary control pulse generator 92, a secondary control pulse generator 94, and an injection pulse synthesizer 96. A

voltage regulator 98 is connected between the unregulated power line 40 and the ground line 42 for providing a regulated supply voltage for the injection pulse generator 84 on a regulated power line 100. The primary control pulse generator 92, the secondary control pulse generator 94, and the injection pulse synthesizer 96 are each connected between the regulated power line 100 and the ground line 42. The voltage regulator 98 may be provided by virtually any suitable voltage regulating apparatus, such as a Zener diode.

Referring to FIGS. 1 and 2, the primary control pulse generator 92 repetitively produces a primary control pulse C p which is initiated in synchronization with the operation of the engine and which is terminated at the expiration of a primary control time period T determined as a preselected function of a primary engine operating parameter. The secondary control pulse generator 94 repetitively produces a secondary control pulse C which is initiated before the termination of the primary control pulse C p and which is terminated after the termination of the primary control pulse C at the expiration of a secondary control time period T, determined as a function of the primary control time period T,,. Further, the secondary control time period T is determined as a preselected function of a secondary engine operating parameter which is multiplicatively related to the primary engine operating parameter and is also determined as a preselected function of a secondary engine operating parameter which is additively related to the primary engine operating parameter.

The injection pulse synthesizer 96 repetitively develops an injection pulse I extending over an injection time period T,- which is initiated in response to the initiation of the primary control pulse C and which is terminated in response to the termination of the secondary control pulse C Therefore, the duration T of the injection pulse 1 is directly related to the duration T of the primary control pulse C and is directly related to the duration T of the secondary control pulse C As previously described, the amount of fuel applied to the engine 10 by the fuel injector 48 is proportional to the duration T,- of the injection pulse 1.

The primary control pulse generator 92 is connected to the timing pulse generator 80 through the timing pulse line 82 and is connected to a pressure sensor 104 through a suitable linkage 106. The pressure sensor 104 communicates with the intake manifold of the engine 10 downstream from the throttle 74 for monitoring the pressure of the air within the intake manifold 20. The primary control pulses C produced by the primary control pulse generator 92 are applied to a primary control pulse line 108. The primary control pulses C are each initiated in response to the initiation of a timing pulse as received from the timing pulse generator 80. The primary control pulses C,, each have a length or duration T defined as a preselected function of the air pressure within the intake manifold 20 as measured by the pressure sensor 104.

The principal function of the illustrated electronic fuel injection system is to regulate the amount of fuel delivered to the engine 10 in response to the amount of air delivered to the engine 10 thereby to maintain a predetermined air-fuel ratio. The pressure of the air within the intake manifold 20 is directly related to the amount of air delivered to the engine 10 as regulated by the throttle 74. The amount of fuel delivered to the engine 10 is directly related to the length T,- of the injection pulses I, which in turn is directly related to the length T of the primary control pulses C,,. Accordingly, the length T,, of the primary control pulses C p is defined by the primary control pulse generator 92 as a preselected direct function of the air pressure within the intake manifold 20 as measured by the pressure sensor 104. Hence, as the intake air pressure increases, the primary control time period T increases to increase the injection timeperiod T,-. Conversely, as the intake air pressure decreases, the primary control time period T decreases to decrease the injection time period T Preferably, the duration T of the primary control pulses C p is a linear or straight-line function of the air pressure within the intake manifold 20. However, it is to be understood that the primary control time period T may be virtually any desired function of the intake air pressure The primary control pulse generator 92 may be provided by a switching circuit including a resistanceinductance timing network for defining the duration T of the primary control pulses C p in accordance with the L/R time constant of the timing network. The inductance of the timing network may be mechanically varied by the pressure sensor 104 acting through the linkage 106 in response to changes in the pressure of the air within the intake manifold 20 thereby to define the length T of the primary control pulses C as a direct function of the intake air pressure. A more detailed description of one embodiment of the primary control pulse generator 92 maay be had by reference to US. Pat. No. 3,623,459.

The secondary control pulse generator 94 is connected to the primary control pulse generator 92 through the primary control pulse line 108. In addition, the secondary control pulse generator 94 is connected to the vehicle battery 36 through the unregulated power line 40 and the ignition switch 38. Further, the secondary control pulse generator 94 is connected to a plurality of temperature sensor lines 1 12, 114 and 116. The first sensor line 112 is connected to an intake air temperature sensor provided by a thermistor 1 18 mounted within the intake manifold 20 of the engine 10 downstream from the throttle 74 for monitoring the temperature of the intake air. The second sensor line 114 is connected to an engine coolant temperature sensor provided by a thermistor immersed within the cooling fluid surrounding the outer surface of the combustion chamber 12 for monitoringthe general temperature of the engine 10 as manifested by the temperature of the engine coolant. The third sensor line 116 is connected to an injected fuel temperature sensor provided by a thermistor 122 mounted to the fuel injector 48 for monitoring the temperature of the injected fuel.

The secondary control pulses C produced by the secondary control pulse generator 94 are applied to a secondary control pulse line 124. The secondary-control pulses C are each initiated sometime between the initiation and the termination of a primary control pulse C p as received from the primary control pulse generator 92. The secondary control pulses C each have a length or duration T defined as a function of the length or duration T of the primary control pulse C,,. In addition, the duration T of the secondary control pulses C is defined as a preselected function of the supply voltage of the vehicle battery 36 as received via the unregulated power line 40. Moreover, the duration T of the secondary control pulses C is defined as a preselected function of the temperature of the engine 10 as represented by the temperature of the intake air sensed by the 7 thermistor 118, the temperature of the engine coolant sensed by the thermistor 120, and the temperature of the injected fuel sensed by the thermistor 122.

As before discussed, the fuel injector 48 includes a plunger 54 which is electromagnetically coupled with a winding 58. The winding 58 is energized for the duration T, of the injection pulses 1. Due to the inherent inductive properties of the plunger 54 and the winding 58, the plunger 54 arrives at a fully opened position home pull-in" time interval after energization of the winding 58 in response to the initiation of an injecton pulse I Similarly, the plunger 54 arrives at a fully closed position some drop-out time interval after deenergization of the winding 58 in response to the termination of an injection pulse 1. Both the pull-in time interval and the drop-out time interval are dependent upon the supply voltage of the vehicle battery 36 in such a manner that, assuming an injection pulse I of constant length T,, the amount of fuel applied to the engine is directly related to the magnitude of the battery supply voltage. The length T,- of the injection pulses I is directly related to the length T of the secondary control pulses C Accordingly, the duration T of the secondary control pulses C, is defined by the secondary control pulse generator 94 as a preselected inverse function of the supply voltage of the vehicle battery 36. Hence, as the battery voltage increases, the secondary control time period T decreases to decrease the injection time period T,-. Conversely, as the battery voltage decreases, the secondary control time period T increases to increase the injection time period T,-.

Assuming a constant mass of air is delivered to the engine 10, the air pressure within the intake manifold is directly related to the temperature of the intake air. In addition, when the engine 10 is relatively cold, the quantity of fuel which is condensed upon the surfaces of the intake manifold 20, the intake valve 22, etc. is inversely related to the temperature of these engine parts as manifested by the temperature of the engine coolant. Further, when the engine is very hot, the quantity of fuel which is vaporized within the intake manifold 20, is directly related to the temperature of the injected fuel, especially the fuel temperature at the nozzle of the fuel injector 48. Therefore, to accurately maintain a predetermined air-fuel ratio, the amount of fuel injected into the intake manifold 20 must be compensated for the effects of temperature upon intake air pressure, fuel condensation, and fuel vaporization.

The amount of fuel applied to the engine 10 is directly related to the length T, of the injection pulses I, which in turn is directly related to the length T, of the secondary control pulses C Accordingly, the length T of the secondary control pulses C is defined by the secondary control pulse generator 94 as a preselected inverse function of the intake air temperature, as a preselected inverse function of the engine coolant temperature, and as a preselected direct function of the injected fuel temperature. Preferably, the temperature of the engine coolant is effective to lengthen the injection time period T, only when such temperature is below a value at which appreciable amounts of fuel are condensed, while the temperature of the injected fuel is effective to lengthen the injection time period T, only when such temperature is above a value at which appreciable amounts of fuel are vaporized.

The structure and operation of one embodiment of the secondary contr'ol pulse generator 94 is illustrated in FIGS. 2 and 3. A capacitor 126 having a capacitance C is connected between a junction 127 and the ground line 42. A control voltage Vis developed across the capacitor 126. A charge circuit 128 is connected to the capacitor 126 at the junction 127 through a charge line 130 and is connected to the primary control pulse line 108. The charge circuit 128 is responsive to the presence of a primary control pulse C p on the primary control pulse line 108 to charge the capacitor 126 with a constant charge current to linearly increase the amplitude of the control voltage V. A discharge circuit 132 is connected to the capacitor 126 at the junction 127 through a discharge line 134 and is connected to the primary control pulse line 108. The discharge circuit 134 is responsive to the absence of a primary control pulse C, on the primary control pulse line 108 to discharge the capacitor 126 with a constant discharge current 1,, to linearly decrease the amplitude of the control voltage V.

A voltage booster 136 includes an NPN junction transistor 138 and a NPN junction transistor 140. The emitter electrode of the transistor 138 is connected directly to the capacitor 126 at the junction 127. The base electrode of the transistor 138 is connected directly to a junction 142. The collector electrode of the transistor 138 is connected directly to the regulated power line 100. The emitter electrode of the transistor 40 is connected directly to the junction 142. The base electrode of the transistor 140 is connected directly to the primary control pulse line 108. The collector electrode of the transistor 140 is connected directly to the ground line 42. A resistor 144 is connected between the junction 142 and the regulated power line 100. A resistor 146 and a temperature compensating diode 148 are connected in series between the junction 142 and the ground line 42.

The transistor 140 is rendered fully conductive in response to the absence of a primary control pulse Cp on the primary control pulse line 108. With the transistor 140 turned on, the junction 142 is effectively clamped to the ground line 42 through the transistor 140. Actually, the voltage level at the junction 142 is maintained above the voltage level on the ground line 42 by an amount equal to the saturation voltage drop of the transistor 140. With the junction 142 effectively clamped to the ground line 42, the transistor 138 is rendered fully nonconductive. With the transistor 138 turned off, it exerts no effect on the amplitude of the control voltage V defined across the capacitor 126.

When a primary control pulse C is initiated on the primary control pulse line 108, the transistor 140 is rendered fully nonconductive. With the transistor 140 turned off, the junction 142 is unclamped from the ground line 42. As a result, the transistor 138 is rendered conductive in an emitter-follower mode to rapidly charge the capacitor 126 to substantially instantaneously increase the amplitude of the control voltage V to an initial level L,-. The initial level L, is equal to the voltage level defined at the junction 142 by the voltage divider action of the resistors 144 and 146 and the diode 148 less the forward biased voltage drop of the base-emitter diode of the transistor 138. Thus, the transistor 138 effectively boosts the amplitude of the control voltage V to the initial level L,- in response to the initiation of a primary control pulse C,,. Simultaneously, the charge circuit 128 begins to charge the capacitor 126 with the constant charge current 1 to increase the amplitude of the control voltage V from the initial level L,. As the control voltage increases above the initial level L,, the transistor 138 is reverse biased.

Further, the secondary control pulse generator 94 includes a differential amplifier or switch 150 including NPN junction transistors 152, 154 and 156. The collector electrode of the transistor 152 is connected directly to a junction 157 between the emitter. electrodes of the transistors 154 and 156. The emitter electrode of the transistor 152 is connected through a biasing resistor 158 to the ground line 42. The base electrode of the transistor 152 is connected directly to a junction 159. A biasing resistor 160 is connected between the junction 159 and the regulated power line 100. A biasing resistor 162 and a temperature compensating diode 164 are connected in series between the junction 158 and the ground line 42. The base electrode of the trantween the junction 166 and the unregulated power line 40. The collector electrode of the transistor 156 is connected directly to the secondary control pulse line 124 at a junction 174. A biasing resistor 176 is connected between the junction 174 and the regulated power line In the differential amplifier 150, the transistor 152 is rendered conductive in a constant current mode through the biasing action of the resistors 158, 160 and 162, and the diode 164. The transistor 152 provides a constant current sink for the switching transistors 154 and 156. In the conventional manner, the differential amplifier 150 is operable between first and second states. In the first state, the transistor 154 is rendered fully conductive while the transistor 156 is rendered fully nonconductive. 1n the second state, the transistor 156 is rendered fully conductive while the transistor 154 is rendered fully nonconductive. A secondary control pulse C is initiated on the secondary control pulse line 124 as the transistor 156 turns off and is terminated on the secondary control pulse line 124 as the transistor 156 turns on.

The differential amplifier 150 switches to the first state when the voltage at the junction 127 exceeds the voltage at the junction 166. Alternately, the differential amplifier switches to the second state when the voltage at the junction 166 exceeds the voltage at the junction 127. The voltage at the junction 127 is provided by the amplitude of the control voltage V defined across the capacitor 126. The voltage at the junction 166 is provided by a final voltage level L, defined by the voltage divider action of the resistors 168, 170 and 172 in direct proportion to the supply voltage of the vehicle battery 36 as received via the unregulated power line 40. In short, the final voltage level .L, at the junction 166 follows the magnitude of the vehicle battery voltage.

At the initiation of a primary control pulse C on the primary control pulse line 108, the discharge circuit 132 is turned off and the charge circuit 132 is turned on to charge the capacitor with the constant charge current 1 to increase the amplitude of the control voltage V from the initial level L, defined by the voltage booster 136. Depending upon the relative magnitudes of the initial level L, and the final level L the differential amplifier 150 switches to either the first state or the second state. If the initial level L,- is greater than the final level L the differential amplifier immediately switches to the first state to initiate a secondary control pulse C at the junction 174. If the final level L; is greater than the initial level L,-, as shown in FIG. 2, the differential amplifier 150 initially switches to the second state in which a secondary control pulse C,- is not produced at the junction 174. Subsequently, as the amplitude of the control voltage V increases above the final level L, under the influence of the charge current 1 the differential amplifier switches to the first state to define a secondary control pulse C on the secondary control pulse line 124.

At the termination of a primary control pulse C on the primary control pulse line 108, the charge circuit 128 is turned off and the discharge circuit 132 is turned on to discharge the capacitor 126 with the constant discharge current I to decrease the control voltages C,. from a peak level L defined at the termination of the primary control pulse C As the amplitude of the control voltage V decreases below the final level L under the influence of the discharge current 1 the differential amplifier 150 switches to the second state to terminate the secondary control pulse C at the junction 174. For reasons which will be more fully explained later,

. the temperature sensor lines 112, 114 and 1 16 are preferably connected to the charge circuit 128 for defining the charge current of the capacitor 126 in inverse relation to the intake air temperature as sensed by the thermistor 118, in inverse relation to the engine coolant temperature as sensed by the thermistor 120, and in direct relation to the injected fuel temperature as sensed by the thermistor 122. Alternately, the temperature sensor lines 112, 114 and 116 may be connected to the discharge circuit 132 for defining the discharge current 1,; of the capacitor 126 in direct relation to the intake air temperature, in direct relation to the engine coolant temperature, and in inverse relation to the injected fuel temperature. Between the extremes of these two examples, it will be apparent that either the charge current I or the discharge current 1,, of the capacitor 126 may be appropriately varied in response to any desired combination of the intake air temperature, the engine coolant temperature, and the injected fuel temperature. The charge circuit 128 and the discharge circuit 132 may be provided by virtually any suitable thermistor controlled constant current sources.

The injection pulse synthesizer 96 is connected to the primary control pulse generator 92 through the primary control pulse line 108 and is connected to the secondary control pulse generator 94 through the secondary control pulse line 124. The injection pulse synthesizer 96 is responsive to the receipt of a primary control pulse C,, and a secondary control pulse C to develop an injection pulse I on the injection pulse line 86. As previously described, the injection pulse I extends over an injection time period T,- which is initiated in response to the initiation of the primary control pulse C,, and which is terminated in response to the termination of the secondary control pulse C in other words, the injection pulse synthesizer 96 develops an injection pulses I in response to the presence of either a primary' control pulse C,, or a secondary control pulse C The fuel injector driver 88 energizes the fuel injector 48 for the duration T, of the injection pulses I emitted by the injection pulse synthesizer 96. Accordingly, the quantity of fuel delivered to the engine 10 is proportional to the length 1 1 T, of the injection pulses l.

The total quantity of fuel Q delivered to the engine 10, which is proportional to the duration T,- of the injection pulses I may be expressed by the following equation:

which indicates that the fuel quantity Q is equal to the primary control time period T plus the time interval defined between the decrease of the control voltage V from the peak level L,, to the final level L, as a result of discharging the capacitance C of the capacitor 126 with the constant discharge current I The peak level L of the control voltage V may be expressed by the following equation:

L, L T (I /C) which indicates that the peak level L is equal to the initial level L, plus the change in the control voltage V produced by charging the capacitance C of the capacitor 126 with the charge current over the primary control time period T,,. The simultaneous solution of equations 1 and 2 for the fuel quantity Q yields the following equation:

which defines a linear or straight-line fuel control curve F as shown in FIG. 4.

Referring to FIG. 4, the fuel control curve F is described within a two-dimensional coordinate system defined by a horizontally disposed X-axis and a vertically disposed Y-axis which perpendicularly intersect at an origin 0. The primary control time period T,,, which is defined as a preselected function of the air pressure within the intake manifold 20, is plotted along the X- axis. The fuel quantity Q is plotted along the Y-axis. The fuel control curve F is characterized by a slope and an offset. The slope of the fuel control curve F is given by the ratio (Y'/x') of the distance Y traced along the Y-axis to the distance x traced along the X-axis when an imaginary point is moved a distance a along the fuel control curve F. The offset of the fuel control curve F is given by the distance b between the origin and the intersection U of the fuel control curve F with the Y- axis. This intersection is only theoretical since the primary control time period T,, is never zero in actual practice.

Referring to equation 3, the slope of the fuel control curve F is defined by the term (1 I /I Changes in the slope term of equation 3, which are defined as a preselected function of the temperature of the engine 10, have the effect of rotating the fuel control curve F about the Y-axis intercept U as depicted by the doubleheaded arrow 178. The offset of the fuel control curve F is defined by the term (L,- L C/I Changes in the offset term of equation 3, which are defined as a preselected function of the supply voltage of the vehicle battery 36, have the effect of vertically shifting the Y-axis intercept U of the fuel control curve F as depicted by the double-headed arrow 180. Depending upon the relative magnitudes of the initial level L, and the final level L, of the control voltage V, the net sign of the offset term (L L C/I may be plus or minus Accordingly, the Y-axis intercept U of the fuel control curve F may be shifted above or below the origin 0. Since the final level L is greater than the initial level L, in FIG. 2, the Y-axis intercept U of the fuel control curve F is appropriately located below the origin 0 in FIG. 4.

The net change in the amount of fuel delivered to the engine as a result of variations in the temperature of the engine 10 is dependent upon the pressure of the air within the intake manifold 20. Given a constant air mass within the intake manifold 20, the intake air pressure is directly proportional to the intake air temperature. Further, the amount of fuel condensation and the amount of fuel vaporization are directly proportional to the quantity of fuel injected into the intake manifold as primarily determined by the intake air pressure. Thus, the intake air temperature, the engine coolant temperature, and the injected fuel temperature are multiplicatively related as engine operating parameters to the intake air pressure. Consequently, the slope (y/.\") of the fuel control curve F should be a function of these various temperatures only. This criteria is satisfied by the slope term (1 1 /1 of equation 3. Preferably, only the charge current 1 is controlled as a function of engine temperature, while the discharge current 1,, is fixed.

The net change in the amount of fuel delivered to the engine 10 as a result of variations in the supply voltage of the vehicle battery 36 is independent of the pressure of the air within the intake manifold 20. Hence, the battery supply voltage is additively related as an engine operating parameter to the intake air pressure. Therefore, the offset b of the fuel control curve F should be a function of the vehicle battery voltage only. Assuming the discharge current l is fixed, this criteria is satisfied by the offset term (L, L C/I of equation 3. The magnitude of the final level L; is controlled as a function of the battery supply voltage.

It is to be understood that the illustrated embodiment of the invention is shown for demonstrative purposes only and that various alterations and modifications may be made to the illustrated embodiment without departing from the spirit-and scope of the invention.

What is claimed is:

1. In an internal combustion engine, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated after a time duration T, determined as a preselected function of a primary engine operating parameter; a capacitor having a capacitance C for developing a control voltage thereacross; means responsive to the presence of a primary control pulse for charging the capacitor with a charge current I to increase the control voltage from an initial level L, defined at the initiation of the primary control pulse to a peak level L defined at the termination of the primary control pulse; means responsive to the absence of a primary control pulse for discharging the capacitor with a discharge current I to decrease the control voltage from the peak level L,, to a final level L;; means for applying fuel to the engine in an amount proportional to the time interval established between the departure of the control voltage from the initial level L, and the arrival of the control voltage at the final level L, so that the total quantity of fuel Q delivered to the engine is defined by the following equation Q p( d) i f) a; means for defining at least one of the charge current 1 and the discharge current I of the capacitor as a preselected function of a first secondary engine operating parameter; and means for defining the difference between the initial level L,- and the final level L, of the control voltage as a preselected function of a second secondary engine operating parameter.

2. In an internal combustion engine including an air supply system for providing intake air to the engine, a battery for providing a supply voltage, and a fuel supply system including at least one voltage responsive fuel injector for applying fuel to the engine when energized by the supply voltage, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated at the expiration of a time duration Tp determined as a preselected function of the pressure of the intake air; a capacitor having a capacitance C for developing a control voltage thereacross; means for charging the capacitor with a charge current I in response to the presence of a primary control pulse to increase the control voltage from an initial level L,- defined at the initiation of the primary control pulse to a peak level L p defined at the termination of the primary control pulse; means for discharging the capacitor with a discharge current 1,; in response to the absence of a primary control pulse to decrease the control voltage from the peak level L to a final level L;; means for energizing the fuel injector with the supply voltage between the departure of the control voltage from the initial level L, and the arrival of the control voltage at the final level L, so that the total quantity of fuel Q applied to the engine is defined by the following equation means for defining at least one of the charge current I and the discharge current 1,, of the capacitor as a preselected function of a temperature of the engine; -and means for defining the difference between the initial level L, and the final level L; of the control voltage as a preselected function of the magnitude of the supply voltage.

3. In an internal combustion engine, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated at the expiration of a time duration T determined as a preselected function of a primary engine operating parameter; a capacitor having a capacitance C for developing a control voltage thereacross; means for charging the capacitor with a charge current I in response to the presence of a primary control pulse to increase the control voltage from an initial level L,- defined at the initiation of the primary control pulse to a peak level L,, defined at the termination of the primary control pulse; means for discharging the capacitor with a discharge current I in response to the absence of a primary control pulse to decrease the control voltage from the peak level L to a final level L]; means for applying fuel to the engine in an amount proportional to the time interval established between the departure-of the control voltage from the initial level L,- and the arrival of the control voltage at the final level L, so that the total quantity of fuel Q applied to the engine is defined by the following equation means for defining the charge current 1 of the capacitor as a preselected function of a secondary engine operating parameter which is multiplicatively related to the primary engine operating parameter; means for defining the difference between the initial level L,- and the final level L, of the control voltage as a preselected function of a secondary engine operating parameter which is additively related to the primary engine operating parameter.

4. In an internal combustion engine including a coolant suppy system for providinga coolant to the engine, an air supply system or providing intake air to the engine, a battery for providing a supply voltage, and a fuel supply system including at least one voltage responsive fuel injector for applying fuel to the engine when energized by the supply voltage, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated at the expiration of a time duration T determined as a preselected direct function of the pressure of the intake air; a capacitor having a capacitance C for developing a control voltage thereacross; means for charging the capacitor with a charge current I in response to the presence of a primary control pulse to increase the control voltage from an initial level L; defined at the initiation of the primary control pulse to a peak level L,, defined at the termination of the primary control pulse; means for discharging the capacitor with a discharge current l in response to the absence of a primary control pulse to decrease the control voltage from the peak level L to a final level L;; means for energizing the fuel injector with the supply voltage between the departure of the control voltage from the initial level L, and the arrival of the control voltage at the final level L, so that the total quantity of fuel Q applied to the engine is defined by the following equation Q a T (l 1 /1 (L; L C/I means for defining at least one of the charge current L and the discharge current I as a preselected function of the temperature of the intake air and a preselected function of the temperature of the engine coolant and a preselected direct function of the temperature of the injected fuel; and means for defining the difference between the initial level L, and the final level L, of the control voltage as a preselected function of the magnitude of the supply voltage. 

1. In an internal combustion engine, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated after a time duration Tp determined as a preselected function of a primary engine operating parameter; a capacitor having a capacitance C for developing a control voltage thereacross; means responsive to the presence of a primary control pulse for charging the capacitor with a charge current Ic to increase the control voltage from an initial level Li defined at the initiation of the primary control pulse to a peak level Lp defined at the termination of the primary control pulse; means responsive to the absence of a primary control pulse for discharging the capacitor with a discharge current Id to decrease the control voltage from the peak level Lp to a final level Lf; means for applying fuel to the engine in an amount proportional to the time interval established between the departure of the control voltage from the initial level Li and the arrival of the control voltage at the final level Lf so that the total quantity of fuel Q delivered to the engine is defIned by the following equation Q NOT = Tp(1 + Ic/Id) + (Li - Lf) C/Id; means for defining at least one of the charge current Ic and the discharge current Id of the capacitor as a preselected function of a first secondary engine operating parameter; and means for defining the difference between the initial level Li and the final level Lf of the control voltage as a preselected function of a second secondary engine operating parameter.
 2. In an internal combustion engine including an air supply system for providing intake air to the engine, a battery for providing a supply voltage, and a fuel supply system including at least one voltage responsive fuel injector for applying fuel to the engine when energized by the supply voltage, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated at the expiration of a time duration TP determined as a preselected function of the pressure of the intake air; a capacitor having a capacitance C for developing a control voltage thereacross; means for charging the capacitor with a charge current Ic in response to the presence of a primary control pulse to increase the control voltage from an initial level Li defined at the initiation of the primary control pulse to a peak level LP defined at the termination of the primary control pulse; means for discharging the capacitor with a discharge current Id in response to the absence of a primary control pulse to decrease the control voltage from the peak level LP to a final level Lf; means for energizing the fuel injector with the supply voltage between the departure of the control voltage from the initial level Li and the arrival of the control voltage at the final level Lf so that the total quantity of fuel Q applied to the engine is defined by the following equation Q not = Tp(1 + Ic/Id) + (Li - Lf) C/Id; means for defining at least one of the charge current Ic and the discharge current Id of the capacitor as a preselected function of a temperature of the engine; and means for defining the difference between the initial level Li and the final level Lf of the control voltage as a preselected function of the magnitude of the supply voltage.
 3. In an internal combustion engine, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated at the expiration of a time duration Tp determined as a preselected function of a primary engine operating parameter; a capacitor having a capacitance C for developing a control voltage thereacross; means for charging the capacitor with a charge current Ic in response to the presence of a primary control pulse to increase the control voltage from an initial level Li defined at the initiation of the primary control pulse to a peak level Lp defined at the termination of the primary control pulse; means for discharging the capacitor with a discharge current Id in response to the absence of a primary control pulse to decrease the control voltage from the peak level Lp to a final level Lf; means for applying fuel to the engine in an amount proportional to the time interval established between the departure of the control voltage from the initial level Li and the arrival of the control voltage at the final level Lf so that the total quantity of fuel Q applied to the engine is defined by the following equation Q not = Tp(1 + Ic/Id) + (Li - Lf) C/Id; means for defining the charge current Ic of the capacitor as a preselected function of a secondary engine operating parameter which is multiplicatively related to the primary engine operating parameter; means for defining the difference between the initial level Li and the final level Lf of the control voltage as a preselected function of a secondary engine operating parameter which is additively related to the primary engine operating parameter.
 4. In an internal combustion engine including a coolant suppy system for providing a coolant to the engine, an air supply system or providing intake air to the engine, a battery for providing a supply voltage, and a fuel supply system including at least one voltage responsive fuel injector for applying fuel to the engine when energized by the supply voltage, the combination comprising: means for producing a primary control pulse initiated in synchronization with the operation of the engine and terminated at the expiration of a time duration Tp determined as a preselected direct function of the pressure of the intake air; a capacitor having a capacitance C for developing a control voltage thereacross; means for charging the capacitor with a charge current Ic in response to the presence of a primary control pulse to increase the control voltage from an initial level Li defined at the initiation of the primary control pulse to a peak level Lp defined at the termination of the primary control pulse; means for discharging the capacitor with a discharge current Id in response to the absence of a primary control pulse to decrease the control voltage from the peak level Lp to a final level Lf; means for energizing the fuel injector with the supply voltage between the departure of the control voltage from the initial level Li and the arrival of the control voltage at the final level Lf so that the total quantity of fuel Q applied to the engine is defined by the following equation Q not = Tp(1 + Ic/Id) + (Li - Lf) C/Id; means for defining at least one of the charge current Lc and the discharge current Id as a preselected function of the temperature of the intake air and a preselected function of the temperature of the engine coolant and a preselected direct function of the temperature of the injected fuel; and means for defining the difference between the initial level Li and the final level Lf of the control voltage as a preselected function of the magnitude of the supply voltage. 